One vertex per element, one color per generator, with an edge from x to x·s.
(2,6)(7,8)(9,10)(11,13)(12,16)(14,22)(15,18)(17,23)(19,24)(20,21)(26,30)(27,33)(32,37)(34,39) involution — undirected(1,2,5,6)(3,7,4,8)(9,11,15,12)(10,16,18,13)(14,19,23,20)(17,24,22,21)(28,35)(32,37)(34,39)(38,40)(1,3,5,4)(2,7,6,8)(9,10)(11,13)(12,16)(14,17)(15,18)(19,21)(20,24)(22,23)(25,26)(27,31)(28,32)(29,30)(33,36)(34,38)(35,37)(39,40)(1,3,5,4)(2,7,6,8)(9,12,15,11)(10,16,18,13)(14,20,23,19)(17,24,22,21)(25,27,29,33)(26,31,30,36)(28,34,35,39)(32,38,37,40)(1,3,5,4)(2,7,6,8)(9,13,15,16)(10,11,18,12)(14,21,23,24)(17,19,22,20)(25,28,29,35)(26,32,30,37)(27,34,33,39)(31,38,36,40)(1,4,5,3)(2,8,6,7)(9,14,15,23)(10,17,18,22)(11,19,12,20)(13,21,16,24)(25,26)(27,31)(28,32)(29,30)(33,36)(34,38)(35,37)(39,40)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.